WorldLeish7
Authors: Armand Balboni
Journal: The Lancet Microbe (2022)

The Seventh World Congress on Leishmaniasis (WorldLeish7) returned in 2022 as an in-person scientific meeting in Cartagena, Colombia with more than 700 masked and COVID-19-protocol adherent participants from 47 countries. The quadrennial conference brings together researchers to discuss ways to identify and aid the 350 million people in 98 countries who are at risk of developing leishmaniasis, a vector-borne parasitic disease transmitted by sandflies and caused by species of trypanosomatid protozoa belonging to the Leishmania genus. Organised and hosted by PECET (Programa de Estudio y Control de Enfermedades Tropicales of the Universidad de Antioquia, Colombia) and sponsored by organisations including DNDi, EOSYNC, The End Fund, WHO, Bill and Melinda Gates Foundation, Care, Liverpool School of Tropical Medicine, and PATH, the 2022 conference included 210 speakers, 44 symposia, eight round tables, four special meetings, and five plenary talks over six days (Aug 1–6, 2022). Aya Yajima (WHO South-East Asia Regional Office, New Delhi, India) provided an optimistic update on efforts to eliminate kala-azar (visceral leishmaniasis) in the endemic regions of India, Nepal, and Bangladesh. Elimination was defined as an annual incidence of less than one case of visceral leishmaniasis per 10 000 population. Yajima highlighted that joint efforts by governmental and non-governmental public health officials within the southeast Asia region have made substantial progress in the elimination of kala-azar with reported cases in the three endemic countries declining from over 50 000 cases in 2007 to 2335 cases in 2020, and subsequently 1577 in 2021. Importantly, it was noted that Bangladesh has sustained the target of less than one visceral leishmaniasis case per 10 000 population. Given the substantial progress made since the launch of the Regional Strategic Framework for Elimination of Kala-azar from the South-East Asia Region in 2012, Yajima stated that WHO SEARO is launching a new strategy for kala-azar to reinforce the regional initiative with a focus on integration to accelerate and sustain elimination of kala-azar in southeast Asia. Nancy Gore Saravia (Centro Internacional de Entrenamiento e Investigaciones Medicas, Cali Colombia), in her talk on parasite drug susceptibility and response to treatment in cutaneous leishmaniasis, described a lack of a comprehensive understanding of the relationship between drug susceptibility of Leishmania spp and chemotherapies for the treatment of cutaneous leishmaniasis. Saravia stated that “this knowledge gap impedes the consideration of resistance in treatment policy or decisions and the optimal use of anti-leishmanial drugs to reduce morbidity”. Her lab evaluated the susceptibility of clinical strains in primary human macrophages and peripheral blood mononuclear cells (PBMCs) compared with the U937 histiocytic cell line used in determining phenotypic susceptibility to antileishmanial drugs. Parasite survival was evaluated by microscopy and quantitative PCR of the Leishmania 7SL RNA gene. The results demonstrated that parasitic resistance to antimony was significantly higher among strains from patients with treatment failure compared with patients that were cured following treatment. Saravia suggested that parasite survival during drug exposure in the ex-vivo and in-vitro models likely reflects the integrity of the inflammatory response of primary macrophages and PBMCs compared with the U937 cell line. Sara M Robledo (PECET, Universidad de Antioquia-Udea, Medellín, Colombia) outlined previous studies containing preclinical data that suggested the use of hederagenin glucoside saponins (SS) and chromane hydrazone (TC2) combined in a 1:1 ratio has high potential for antileishmanial therapy because both compounds alter the survival of Leishmania spp and the ability to infect adjacent macrophages. Robledo went on to show development of an ointment formulation containing 2% TC2 and 2% SS (w/w) for cutaneous leishmaniasis. Treatment with 2% TC2 and 2% SS ointment produced a complete long-term clinical cure in 10 patients and 56 dogs without any serious adverse effects. Robledo and her colleagues have produced results that support further clinical studies to investigate the safety and efficacy of the use of this therapy for the treatment of cutaneous leishmaniasis. WorldLeish7 provided a much needed forum for the presentation of scientific and clinical data for this neglected tropical disease. Additionally, the Plenary Talks by Jorge Alvar (DNDi) on visceral leishmaniasis elimination, Paul Kaye (University of York, York, UK) on molecular pathology and stratification of leishmaniasis, and Byron Arana (DNDi) on the future of cutaneous leishmaniasis treatment, presented a summary of the research that is needed to guide governments, NGOs, and philanthropic institutions on reducing and treating cases of leishmaniasis. A particularly powerful and data-driven talk by Koert Ritmeijer (Médecins Sans Frontières) spoke of the role of armed conflict in the development of acute and endemic leishmaniasis by presenting 2005–18 data that shows a 4-times increase in reported cutaneous leishmaniasis cases in regions of the Middle East and north Africa with conflict and internal displacement. His talk was a call for further institutional support for eliminating the disease. For more on WorldLeish7 see https://www.worldleish7.org/ For more on WorldLeish7 see https://www.worldleish7.org/